U.S. patent application number 14/407115 was filed with the patent office on 2015-05-14 for method and equipment for measuring the filter sectors in disc filters.
The applicant listed for this patent is Nicholas Rowe. Invention is credited to Nicholas Rowe.
Application Number | 20150128434 14/407115 |
Document ID | / |
Family ID | 49509782 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150128434 |
Kind Code |
A1 |
Rowe; Nicholas |
May 14, 2015 |
METHOD AND EQUIPMENT FOR MEASURING THE FILTER SECTORS IN DISC
FILTERS
Abstract
The method and equipment relates to the measurement of
deflections of filter sectors in a disc filter. The filter discs in
the disc filter are constituted by a number of filter sectors, and
the distance between a position fixed relative to the filter, most
commonly the scraper itself, and the filter surface is
conventionally measured by manual measurement methods. The
equipment is instead used that has a measuring head with a
quick-release coupling for its mounting fixed in the filter, and a
position sensor in the measuring head that measures the distance
between the measurement arrangement and the surface of the filter
disc in order to form momentary measurement results. The momentary
measurement results are transferred by a data transfer link from
the measurement arrangement to a data collection unit PC that has a
memory.
Inventors: |
Rowe; Nicholas; (Karlstad,
SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rowe; Nicholas |
Karlstad |
|
SE |
|
|
Family ID: |
49509782 |
Appl. No.: |
14/407115 |
Filed: |
June 12, 2013 |
PCT Filed: |
June 12, 2013 |
PCT NO: |
PCT/SE2013/050684 |
371 Date: |
December 11, 2014 |
Current U.S.
Class: |
33/533 |
Current CPC
Class: |
G01B 5/30 20130101; G01B
3/22 20130101; D21C 9/06 20130101; B01D 33/21 20130101; G01B 5/20
20130101 |
Class at
Publication: |
33/533 |
International
Class: |
B01D 33/21 20060101
B01D033/21; G01B 3/22 20060101 G01B003/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 12, 2013 |
SE |
1250623-4 |
Claims
1. A method for the measurement of the deflections of a filter
sector in a disc filter, where the disc filter consists of at least
one filter disc arranged at a rotating hollow shaft, which filter
disc is constituted by at least 10 hollow filter sectors, each one
of which is covered by a filter element and has a hollow filter
mounting that is connected to the rotating hollow shaft in order to
lead away the filtrate that has collected in the filter sectors,
and where a fixed support frame that is independent of the filter
disc is present mounted at a distance from each filter disc
comprising: a measuring head is mounted at the support frame with a
measurement arrangement in the measuring head that measures the
distance between the measurement arrangement and the surface of the
filter disc, the hollow shaft is rotated while the measurement
arrangement measures the distance between the measuring head and
the surface of the filter disc at at least two measuring points on
each filter sector, and the measured values that have been
collected are stored in a data collection unit (PC) connected to
the measuring head, after which the measurement results that have
been collected are used to determine the current deflections of
individual filter sectors and to constitute the information on
which adjustment of the filter sectors in order to minimise the
deflections is based.
2. The method according to claim 1, wherein measuring points that
have been collect are coupled with a unique filter sector.
3. The method according to claim 2, wherein the measuring points
that have been collected are coupled to a unique filter sector by
synchronisation of the rotation of the hollow shaft with the
collection of the measurements.
4. The method according to claim 2, wherein the measuring points
that have been collected are coupled to a unique filter sector by
detecting the start and end of a filter sector and by collecting
the measurements across the relevant filter sector.
5. Equipment for the measurement of the deflection of a filter
sector in a disc filter, comprising: the disc filter consists of at
least one filter disc arranged on a rotating hollow shaft, which
filter disc is constituted by at least 10 hollow filter sectors
each one of which is covered by a filter element and has a hollow
filter mounting that is connected to the rotating hollow shaft in
order to lead away filtrate that has collected in the filter
sectors, and where a fixed support frame that is independent of the
filter disc is mounted at a distance from each filter disc, the
equipment comprises a measuring head with a quick release coupling
by which it is mounted on the support frame, a position sensor in
the measuring head that measures the distance between the
measurement arrangement and the surface of the filter disc in order
to form the momentary measurement result, a data transfer link for
the transfer of momentary measurement results from the measurement
arrangement, a data collection unit (PC) connected to the
measurement arrangement through the data transfer link with a
memory for the storage of momentary measurement results, and
synchronisation means for the coupling between momentary
measurement results and the individual filter sectors while the
hollow shaft is rotating.
6. The equipment according to claim 5, wherein the measuring head
comprises a pre-stressed measurement probe that is held against the
surface of the filter disc by a spring and that follows the surface
of the filter disc continuously.
7. The equipment according to claim 6, wherein the tip of the
measurement probe that is in contact with the surface of the filter
disc is constituted by a running wheel that rolls on the surface of
the filter disc.
8. The equipment according to claim 7, wherein the transition
between two filter sectors forms a depression in the surface of the
filter disc with a radius R.sub.1 at the edge of the filter sector
in intervals 5-20 mm, which edge radii form the depression, the
running wheel has a radius that is in the interval 1-5 times larger
than R.sub.1.
Description
TECHNICAL AREA
[0001] The present invention concerns a method and equipment for
the measurement of filter sectors in disc filters according to the
introduction to claim 1 and claim 5, respectively.
THE PRIOR ART
[0002] Disc filters are used at several process positions in a
paper pulp mill, not only as fibre filters but also as filters in
the causticisation process.
[0003] Fibre suspensions are dewatered in fibre filters and the
collected fibre cake that forms on the filter discs during one
rotation is scraped off in its entirety.
[0004] Disc filters are used in the causticisation during chemical
recycling, however, in a completely different manner, where a
technology known as "precoating" of the filter surface is most
often used. Independently of whether the filters are green liquor,
white liquor or lime sludge filters, it is not possible to reach
the desired purity of the filtrate (green liquor, white liquor or
washing fluid) without first coating the filter surface with a
layer of lime sludge. The filter surface is most often a fine-mesh
cloth held in tension across a perforated metal frame, although
this cloth can permit small particles of lime sludge to pass. At
the same time as the mesh of the cloth must be fine, it must not
produce too large pressure drop, since this limits the filtration
capacity. The layers of lime sludge on the filter surface will in
this case function as an extra filter element, and these layers are
most often built up by a careful increase in the pressure drop
across the filter surface, before the filtration can start and give
a filtrate of the desired purity. The technique means that the
layers of lime sludge will capture most of the lime sludge
particles in the process fluid that is to be filtered, but it
eventually leads to the surface of the layers of lime sludge
becoming clogged and needing to be renewed. This is normally done
by the use of a knife in which an operator scrapes away the
uppermost, clogged, surface of the layers of lime sludge. During
start-up, first a completely new layer of lime sludge of a given
thickness is formed, after which 5-10% of the thickness is removed
at the subsequent scraping after a few hours of operation, and this
occurs 4-5 times until the layer of lime sludge has reached a
minimum permitted thickness. A new layer of lime sludge is then
built up.
[0005] One problem with these disc filters with precoating is that
the pressure drop, and thus the filtration capacity, is directly
dependent on the thickness of the layer of lime sludge. Since the
disc filters are built up from filter sectors that are fastened to
a hollow shaft, the settings of the individual filter sectors may
differ. An individual filter sector may, for example, be rotated in
the filter housing such that, for example, the forward edge (seen
in the direction of rotation) is positioned at a greater distance
from a scraper than the rear edge. The layers of lime sludge at the
forward edge will then become thicker than at the rear edge, and
the pressure drop will for this reason be higher at the forward
edge. Furthermore, the complete filter surface in a filter sector
may be positioned lower than other filter sectors. The layer of
lime sludge on this lower filter sector will then become thicker
than on other filter sectors, and the pressure drop will for this
reason be higher, which will result in a lower filtration
capacity.
[0006] For the measurement and monitoring of the deflections in
these filter sectors, a time-consuming manual procedure has been
used in which the distance between the scraper and the filter
sector is measured by rulers while the disc filter is rotated
stepwise to a new measurement position. Such measurement of a disc
filter with more than 10 filter discs with 18-20 filter sectors has
required some 1-2 working days. The measurement process is also
associated with risks for the personnel since it is necessary to
measure inside a machine with cramped space while the disc filter
is rotated, and where the distance between a sharp scraper and the
surface of the filter is measured using a ruler. Since the
measurement process is time-consuming, the complete production line
must also be closed down during this period, and this causes a
large loss of income for the paper pulp mill.
THE PURPOSE OF THE INVENTION
[0007] A first purpose of the invention is to be able to minimise
the duration of interruption in operation for the paper pulp mill
while the disc filters are measured.
[0008] A second purpose is to obtain a more reliable measurement of
the disc filters than is possible to obtain by measurement with a
ruler and taking notes of the deflections in a list.
[0009] A third purpose is to be able to obtain a rapid measurement
of the disc filter with stored measurement results that can be
evaluated at a later time. The measurement may in certain cases
show that the filter sectors have deflections that lie within
acceptable limits, and it will in this case be possible to omit the
adjustment operation. If it is revealed during the evaluation that
certain filter sectors have too great deflection, it is possible to
plan adjustments only for the particular filter sectors that
require adjustment.
[0010] A fourth purpose is to be able to obtain a documented
measurement of the disc filters before adjustment, and a verifying
measurement of the disc filters after adjustment of the filter
sectors that require adjustment.
[0011] A fifth purpose is to be able to obtain a documented
measurement of the deflections of filter sectors in a disc filter
such that it is possible to calculate the filtration capacity in
the disc filter, which capacity depends on the pressure drop across
each part of a filter sector and between different filter
sectors.
[0012] A sixth purpose is to verify the current deflections of the
filter sectors of the disc filter such that it is possible to
influence the scraping function in the disc filter so that this can
be optimised and obtaining a safe margin against the scraper not
reaching the surface of the filter and damage it.
BRIEF DESCRIPTION OF THE INVENTION
[0013] The method according to the invention is used for the
measurement of the deflection of a filter sector in a disc filter.
The disc filter consists of at least one filter disc arranged on a
rotating hollow shaft, which filter disc is constituted by at least
10 hollow filter sectors, each one of which is covered by a filter
element and has a hollow filter mounting that is connected to the
rotating hollow shaft in order to lead away filtrate that has
collected in the filter sectors. A fixed support frame that is
independent of the filter disc is mounted at a distance from each
filter disc. The method is characterised in that a measuring head
is mounted on the support frame with a measurement arrangement in
the measuring head that measures the distance between the
measurement arrangement and the surface of the filter disc. The
hollow shaft is rotated while the measurement arrangement measures
the distance between the measuring head and the surface of the
filter disc at at least two measuring points for each filter
sector. The measured values that are obtained are stored in a data
collection unit connected to the measuring head, after which the
measurement results collected are used to determine the current
deflections of individual filter sectors and to constitute the
information on which adjustment of the filter sectors to minimise
the deflections is based.
[0014] It is possible with this method to replace a lengthy manual
measurement process by a rapid collection of data that gives all of
the information required to determine the current status of the
filter deflection and to constitute the information on which to
base a subsequent selective adjustment of the particular filter
sectors that have the greatest deflection.
[0015] According to preferred embodiments of the method, the
collected measuring points are coupled to a unique filter sector.
It is appropriate that this take place through the collected
measuring points being coupled to a unique filter sector through
synchronisation of the rotation of the hollow shaft with the
collection of the measurements. By using the changes of shape
between the filter sectors, it is possible to couple the collected
measuring points to a unique filter sector by detecting the start
and end of a filter sector and by collecting the measurements
across the relevant filter sector.
[0016] The equipment according to the invention is used to measure
the deflection of a filter sector in a disc filter. The disc filter
consists of at least one filter disc arranged at a rotating hollow
shaft. The filter disc is constituted by at least 10 hollow filter
sectors, each one of which is covered with a filter element and has
a hollow filter mounting that is connected to the rotating hollow
shaft in order to lead away the filtrate that has collected in the
filter sectors. Furthermore, a fixed support frame that is
independent of the filter disc is mounted at a distance from each
filter disc. The equipment is characterised in that it comprises
[0017] a measuring head with a quick-release coupling by which it
is mounted on the support frame, [0018] a position sensor in the
measuring head that measures the distance between the measurement
arrangement and the surface of the filter disc in order to form the
momentary measurement result, [0019] a data transfer link for the
transfer of momentary measurement results from the measurement
arrangement, [0020] a data collection unit connected to the
measurement arrangement through the data transfer link with a
memory for the storage of momentary measurement results, and [0021]
synchronisation means for the coupling between momentary
measurement results and the individual filter sectors while the
hollow shaft is rotating.
[0022] According to preferred embodiments of the equipment, the
measuring head may comprise a pre-stressed measurement probe that
is held against the surface of the filter disc by a spring and that
follows the surface of the filter disc continuously. It is
appropriate also that the tip of the measurement probe that is in
contact with the surface of the filter disc is constituted by a
running wheel that rolls on the surface of the filter disc. It is
appropriate that the running wheel has a radius that is in the
interval 1-5 times larger than R.sub.1, in one special embodiment
that exploits the changes of shape of the filter disc between
filter sectors, where the transition between two filter sectors
forms a depression in the surface of the filter disc with a radius
R.sub.1 at the edge of the filter sector in intervals 5-20 mm,
which edge radii form the depression.
DESCRIPTION OF DRAWINGS
[0023] FIG. 1 shows in perspective a typical disc filter for the
filtration of white liquor in the causticisation process,
[0024] FIG. 2 shows in side view a filter disc for a disc
filter,
[0025] FIG. 3 shows a part of a filter disc with three filter
sectors,
[0026] FIG. 4 shows in perspective the appearance of a scraper
arrangement above a lime sludge chute in a disc filter,
[0027] FIG. 5 shows the measuring equipment according to the
invention installed in a disc filter,
[0028] FIG. 6a shows how the filter sectors can be set with either
a twist at the filter mounting or a displacement from the ideal
position,
[0029] FIG. 6b shows the filtration flow through the filter sectors
as a function of the thickness of the layer of lime sludge,
[0030] FIG. 7 shows one type of measurement protocol stored in the
measuring equipment for the detection of deflections in individual
filter sectors, and
[0031] FIG. 8 shows a supplementary type of measurement protocol
stored in the measuring equipment for the detection of twisting in
individual filter sectors.
DETAILED DESCRIPTION OF THE INVENTION
[0032] FIG. 1 shows a disc filter 1, here in the form of a disc
filter under pressure in which the discs are inside a pressure
vessel. The pressure vessel has been drawn partly opened in the
drawing in order to show four filter discs, which are fixed
arranged on and co-rotating with a shaft 10. A lime sludge chute 12
is located between the discs 11, on the upper edge of which chute
is located a scraper 18 parallel to the surface of the discs. Lime
sludge that is scraped from the filter falls into the lime sludge
chute 12, down to the chute connection pipe 13 and onwards to a
collection pipe 14, before the lime sludge finally reaches the lime
sludge tank 3. Pure filtrate, white liquor in the case in which
this is a white liquor filter, passes through the surfaces of the
discs and is led down to the shaft 10, which is a conventional
hollow shaft, and onwards through the filtrate line 20 to a
filtrate tank 2. This drawing shows a filter with 11 filter discs.
The drawing shows also a regulator arm 17 for the scraper
mechanism, inspection hatches 15 through which it is possible to
monitor the function, and manholes 16 that can be opened to obtain
access for any service or adjustment of the discs, scrapers or
filter cloths that may be required.
[0033] FIG. 2 shows a filter disc in a side view, which filter disc
is built up from a number of filter sectors 30. The drawing shows a
filter made up from 20 filter sectors. Each filter sector 30 is
fixed mounted at the hollow shaft 10 through a filter mounting 31
in the form of a pipe 31a that is inserted through a corresponding
drilled hole in the hollow shaft 10. The filter maintains a level
of causticised white liquor just under the upper edge of the lime
sludge chute 12, and the filter disc and the hollow shaft rotate in
the direction denoted by "ROT" such that the lime sludge that has
collected on the surface of the filter can be scraped off with the
scraper 18. The filter contain a number of addition points for
washing liquid and dilution liquid at various positions, and the
following are shown in the drawing: a connection 40a for washing
liquid that is spread over the filter by a pipe 40b provided with a
nozzle, a connection 41a for chute dilution liquid that is spread
at the upper edge of the chute by a pipe 41b provided with a
nozzle, and a connection 42a for cake removal liquid that is spread
over the filter by a pipe 42b that is provided with a nozzle. There
is present also at least one airlift pump 43b that is connected to
a line 43a with air under pressure, which provides stirring at the
bottom of the vessel such that sedimentation of lime sludge is
counteracted. It can here be seen that it is possible to gain
access to the complete mechanism of the scraping function through
the manhole cover 16.
[0034] FIG. 3 shows a part of a filter disc with three filter
sectors 30. Each filter sector 30 is built up from a first inner
perforated metal frame 32, which is in turn covered with a first
coarse filter cloth 33 and a fine filter cloth 34 that lies on top
of it. The perforated metal frame 32 surrounds a hollow compartment
that receives the filtrate that has passed the filter surface,
which hollow compartment is connected to a pipe 31a that leads the
filtrate down into the hollow shaft 10. The pipe 31a is mounted in
a drilled hole in the hollow shaft where the pipe is first pressed
down into the drilled hole after which the filter sector is turned
such that fastening lugs 35 grip bolts 36, which are subsequently
tightened. These fastening lugs allow a certain amount of
adjustment of the rotational position of the filter sector such
that the forward edge 38 can be placed in the same radial plane as
the rear edge (which minimises deflection across the filter
sector). A view seen from below the filter mounting 31 is shown in
Box A. A cross-section seen though X-X in the drawing is shown in
Box B, where the transition between two filter sectors is shown.
This transition between filter sectors has a radius R.sub.1 in
order to minimise loading at the edges of the filter cloths.
[0035] FIG. 4 shows the appearance of a scraper arrangement above a
lime sludge chute 12 in a disc filter. A regulator arm 17 for the
scraper mechanism can be influenced by a servo unit 19, preferably
a hydraulic cylinder or an air cylinder. The regulator arm 17
influences the position of the scraper 18 relative to the surface
of the filter through a linkage 20a-20b-20c in a conventional
manner. Several links 20b for the influence of several scrapers can
be activated at the same time through an adjustable support rod
20c.
[0036] FIG. 5 shows the measuring equipment according to the
invention installed in a disc filter. The equipment comprises
measuring heads 70 with a quick-release coupling for mounting on a
suitable fixed support frame in the disc filter. In the embodiment
shown, the pipe 41b that is equipped with nozzles is used as this
support frame, but any other stationary structure can be used as
support frame for the measuring equipment. In a simple embodiment
shown in the drawing, the quick-release coupling can be constituted
by two fixed shanks 50a and 50b that have an arrangement that has
the nature of a screw clamp for attachment across the support frame
with the handle 52.
[0037] The measuring head 60-61-62 is located on a bracket 51 that
is fixed arranged at the shanks 50a/50b, which measuring head in
the embodiment shown is an electromechanical measuring head with a
running wheel 61 that rolls on the surface of the filter disc or
filter sectors. The running wheel is placed under tension against
the surface of the filter by a spring 62 such that this running
wheel follows the surface of the filter continuously. As is shown
in FIG. 3B, the transition between two filter sectors can form a
depression in the surface of the filter disc with a radius R.sub.1,
in the interval 5-20 mm, at the edge of the filter sector, which
edge radii form the depression, and for this reason it is
appropriate that the running wheel be given a radius that is in the
interval 1-5 times larger than R.sub.1, in order not to fasten in
the depression, while at the same time still being capable of
detecting the passage of a depression and the transition to the
next filter sector.
[0038] The position sensor is located in a housing 60 and detects
the position at the shaft, which is connected to the holder of the
running wheel.
[0039] As an alternative to an electromechanical measuring head, an
optical measurement of distance can be used, for example one with
laser measurement, which will not cause any wear of the filter
cloth.
[0040] The signal from the position sensor can be transferred by a
data transfer link 71 connected to a suitable data collection unit
PC. Alternatively, the data transfer can take place in a wireless
manner using, for example, bluetooth, and the measuring head may
have an integrated source of power or a battery. As is shown in the
drawing, the data collection unit PC may be a conventional laptop
computer that contains memory for the storage of measurement
results that have been collected.
[0041] It is possible with this equipment to implement a rapid
method for the measurement of the deflections of filter sectors in
a disc filter. The measuring head 61-62-63 is mounted on the
support frame 41b with a position sensor 60 in the measuring head
that measures the distance between the measurement arrangement and
the surface of the filter disc. It is appropriate that the
measuring head be placed in a measurement position indicated by MP
in FIG. 2, i.e. close to the periphery of the disc, such that the
measurement is carried out on a measurement circle MC, indicated by
a dashed circle. The hollow shaft 10 is rotated while the
measurement arrangement measures the distance between the measuring
head and the surface of the filter disc at at least two measuring
points for each filter sector. The measured values that are
obtained are stored in a data collection unit connected to the
measuring head, after which the measurement results collected are
used to determine the current deflections of individual filter
sectors and to constitute the information on which adjustment of
the filter sectors to minimise deflection is based. The measurement
can be carried out in a number of ways, but it is advantageous that
the measuring points that have been collected are coupled to a
unique filter sector 30. This can be carried out manually, such
that the collection of measurement results is started when the
measuring head comes into contact with a marked filter sector, and
ended when the marked filter sector returns after rotation of the
hollow shaft by one complete revolution.
[0042] Alternatively, the collected measuring points can be coupled
to a unique filter sector through synchronisation of the rotation
of the hollow shaft with the collection of the measurements.
[0043] Since the transition between filter sectors may have a
depression, the measuring equipment can automatically detect this
transition at the start and end of a filter sector and it can
subsequently store the collected measurement results for this
filter sector.
[0044] FIG. 6a shows the principle of how the filter sectors 30a,
30b and 30c can be set with either a twist .alpha. at the filter
mounting, as is shown for the filter sector 30a or a displacement
from the ideal position, as is shown for the filter sector 30c.
Filter sector 30b is shown here without any deflection, set such
that the precoating layer PS forms ideal thickness Id. For the
twisted filter sector 30a, it is shown that the precoating layer
acquires at its forward edge (relative to the direction of rotation
ROT) an undesired increase Ka+, while it acquires at the rear edge
an undesired reduction Ka-. For the displaced filter sector 30c,
the precoating layer acquires an undesired increase D+ of its
thickness. The type of the deflection of the filter sectors is
shown in the drawings in principle, and a combination of the
deflections that are shown for the filter sectors 30a and 30c can
be present in one filter sector.
[0045] FIG. 6b shows the filtration flow Q through the filter
sectors is influenced as a function of the thickness of the layer
of lime sludge in FIG. 6a. The flow Q is given by the function:
Q = K .DELTA. P .mu. L ##EQU00001##
where K is the permeability of the filtercake or precoating,
.DELTA.P is the pressure drop across the filter cake, .mu. is the
viscosity of the white liquor, and L is the thickness of the filter
cake or precoating. It is thus possible to use this flow equation
to calculate the total flow through a disc filter with the
deflections of the filter sectors that have been measured.
[0046] It is shown that the momentary flow Q.sub.MOM is largest at
the rear edge of the filter sector 30a with a thickness of the
layer of precoating that is too small, due to the thinnest
precoating. The momentary flow across this filter sector then falls
as the forward edge of the filter sector is approached. There is no
open filter surface at the transition to the next filter sector
30b, for which reason the flow falls momentarily. The flow through
the filter sector 30b is constant at all times, since the thickness
of the layer of precoating is constant. The flow through the filter
sector 30c, however, is reduced since the layer of precoating is
much thicker. It is made clear that the filtration capacity in the
form of filtrate flow is influenced to a large extent, depending on
the deflections of the filter sectors that are present.
Furthermore, the purity of the filtrate is influenced when the
precoating varies.
[0047] FIG. 7 shows a measurement protocol after use of the
measuring equipment. A measurement has here been carried out on a
disc filter with nine filter discs, DISC 1-DISC 9, and a
representative measurement in the form of a mean value has been
stored for each filter sector, #1-#20, both on the filtrate side FS
(where the filtrate tank 2 is located) and on the driving side
(where the motor drive is located). In the summary under
measurement data, the maximal measurement, Max, and the minimum
measurement, Min, are presented for each filter disc, with a mean
value AVE that has been formed for these measurements and the
spread DEV between the maximum and the minimum measurements. It can
be seen from the measurement data that filter disc 1, DISC 1, and
filter disc 5, DISC 5, have the greatest spread between the minimum
and the maximum measurements, with spreads of 4.2 mm and 5.1 mm,
respectively, on the driving side (DS) of the filter disc.
[0048] It is possible to determine which filter discs and which
filter sectors are to be adjusted, on the basis of the measurement
results that have been collected. If an acceptable spread of the
deflections of the filter discs is 4.0 mm, it can be seen that
filter disc 1 and filter disc 5 have a larger maximal
spreads/deflections of 4.2 mm and 5.1 mm, respectively.
[0049] If filter disc 1, DISC 1, is to be adjusted in order to
minimise the spread of deflections of the filter discs, it can be
seen that: [0050] filter sector #4 has the lowest measurement
(14.6) on the filtrate side, and also the greatest measurement
(18.1) on the driving side, while filter sector #16 also has the
smallest measurement (14.7) on the filtrate side and the greatest
measurement (17.5) on the driving side. [0051] filter sector #10
has not only the smallest measurement (13.9) on the driving side
but also the greatest measurement (18.5) on the filtrate side, and
that filter sector #14 has not only the smallest measurement (14.0)
on the driving side but also the greatest measurement (18.6) on the
filtrate side.
[0052] Thus, in order to reduce the spread for filter disc 1,
filter sectors #4, #10, #14 and #16 are to be adjusted.
[0053] It is in the same way possible to see that for filter disc
5, filter sectors #2, #4, #7, #11 and #17 are to be adjusted, since
#4 and #7 have spreads that are close to the maximum on the driving
side, and since the others have spreads that are close to the
maximum measurement on the filtrate side.
[0054] Adjustment of the filter sectors proceeds by first loosening
the locking plates (not shown in the drawings) that are located
between the filter sectors at their outer edges, and either bending
the filter sectors into their place in the disc filter or also
loosening the filter mounting and removing the filter sectors such
that they can be realigned in a realignment device. Alternatively,
exchange sectors can be used.
[0055] FIG. 8 shows a supplementary measurement protocol for the
protocol shown in FIG. 7, after use of the measuring equipment.
Here, only measurement results from one filter disc, DISC 5, on the
filtrate side FS are shown, for the three first filter sectors
#1-#3. As is made clear by the measurement protocol in FIG. 7, the
mean values of the distance to the filter sector for the first
three filter sectors #1-#3 were 16.3, 17.0 and 14.7, respectively.
It can here be seen that filter sector #1 has a twist a of 0.8 mm
from forward edge to rear edge of the filter sector, similar to the
pattern of twisting shown for filter sector 30a in FIG. 6a. Filter
sector #2,however, lies plane, without twisting, since the forward
edge and the rear edge are at the same distance, 17.0 mm. Filter
sector 3, however, has a much larger twist .alpha. of -5.0 mm from
the forward edge to the rear edge of the filter sector, similar to
the above-mentioned pattern of twisting shown for filter sector 30a
in FIG. 6a. If an acceptable twisting for the deflection of the
filter discs is 4.0 mm, it can be seen that filter sector #3 must
be adjusted. This is achieved by first loosening the locking plates
(not shown in the drawings) that are located between the filter
sectors at its outer edge, and loosening also the filter mounting,
after which the filter sector is rotated at its bottom, the fixing
screws 36 are tightened and the locking plates are remounted.
[0056] The invention is not limited to the embodiments revealed
above in which measurement results that have been collect are used
to determine the deflections of filter sectors and their twists. It
is possible in theory to use measurements collected before and
after the adjustment to calculate the influence of the flow
capacity of a complete filter disc and the complete disc filter and
the improvement of the capacity that has been achieved. The
measuring head can be placed also in a further measurement position
closer to the hollow shaft, for example at half of the radius of
the measurement circle MC in FIG. 2. This can be done if, for
example, it is suspected that filter sectors are distorted when
considered from the filter mounting out towards the filter
periphery. Since the equipment can carry out the measurement
rapidly and easily, validation of whether the filter sectors are
plane or whether they need adjustment is obtained for a small extra
consumption of time.
* * * * *